Em novembro, a Ana passa a estudar em casa porque o tempo fica mais frio.

In European Portuguese, it is very common to put the definite article before a person’s first name: a Ana, o João, a Maria.

So a Ana does not mean something unusual like the Ana in normal English. It is just standard Portuguese usage, especially in Portugal.

A few quick examples:

• A Ana chegou. = Ana arrived.
• O Pedro está em casa. = Pedro is at home.

This is one of the first things English speakers notice, because English normally does not use an article before someone’s name.

Passar a + infinitive means to start to, to begin to, or to come to do something.

So a Ana passa a estudar em casa means that this becomes her new habit or new situation: before, she did not study at home, and now she does.

This structure often emphasizes a change:

• passa a estudar = starts studying / begins to study
• passa a viver em Lisboa = starts living in Lisbon
• passa a trabalhar de manhã = starts working in the morning

It is a very useful structure in Portuguese.

Because after passar, Portuguese uses the pattern passar a + infinitive.

So:

• passa a estudar
• passa a viver
• passa a fazer

The a here is required by the verb pattern. It is similar to how some English verbs need a certain structure after them. For example, in English you say start studying or begin to study; in Portuguese, with passar, you say passar a estudar.

Em casa is the normal idiomatic way to say at home.

So:

• estudar em casa = to study at home
• ficar em casa = to stay at home
• estar em casa = to be at home

You use na casa when you mean in the house or at someone’s house, usually with a more specific idea:

• na casa da Ana = at Ana’s house
• na casa grande = in the big house

So in this sentence, em casa is correct because it means at home, not in a particular house.

Here porque means because, so it is written as one word.

• porque = because

This is different from:

• por que = why / for which reason, in some question structures
• porquê = the reason / the why, used as a noun

Examples:

• Ela fica em casa porque está frio. = She stays at home because it is cold.
• Por que estás em casa? = Why are you at home?
• Não sei o porquê. = I do not know the reason.

So in your sentence, porque is simply the conjunction because.

In Portuguese, tempo can mean both time and weather. The context tells you which meaning is intended.

Here, because the sentence talks about it becoming colder, o tempo clearly means the weather.

Examples:

• Não tenho tempo. = I do not have time.
• O tempo está bom. = The weather is nice.

This is very normal in Portuguese, even though it feels strange at first to English speakers.

Ficar often means to become or to get, while ser means to be.

So:

• fica mais frio = gets colder / becomes colder
• é mais frio = is colder

In this sentence, the idea is a change in the weather, so ficar is the natural choice.

Compare:

• No inverno, o tempo fica mais frio. = In winter, the weather gets colder.
• Portugal é mais frio do que Malta. = Portugal is colder than Malta.

So fica is used because the weather is changing.

Because frio agrees with o tempo, and tempo is a masculine singular noun.

So:

• o tempo fica mais frio
• a temperatura fica mais fria

The adjective changes to match the noun it describes. Since tempo is masculine singular, the adjective is frio.

This is basic adjective agreement in Portuguese.

Portuguese often uses the present tense to talk about:

• general truths
• regular habits
• seasonal patterns
• events presented as a normal fact

So this sentence can describe what happens when November comes around: Ana starts studying at home because the weather gets colder.

It does not necessarily mean that the action is happening at this exact moment. It can describe a repeated or typical situation.

If you wanted a past meaning, you might say:

• Em novembro, a Ana passou a estudar em casa porque o tempo ficou mais frio.

That would mean it happened in the past.

In Portuguese, the names of months are normally written with a lowercase letter:

• janeiro
• fevereiro
• novembro

This is different from English, where months are capitalized.

So Em novembro is the normal Portuguese spelling.

Putting Em novembro at the beginning gives the time frame first. This is very natural in Portuguese and is similar to English sentences like In November, Ana starts studying at home...

It helps set the scene before the main information.

You could also say:

• A Ana passa a estudar em casa em novembro porque o tempo fica mais frio.

That is still grammatical, but starting with Em novembro sounds very natural when you want to highlight the time.